1. Field of the Invention
The present invention relates to a blood sampler of the suction type useful for sampling from a human skin a predetermined quantity of blood for various blood tests, by thrusting a sting or needle into the human skin, wherein a vacuum of a certain degree is applied thereto to suck the blood sample into the device.
2. Description of Prior Art
Generally, so-called lancet injectors comprise a blade and a pressable end opposed thereto, with the blade having an acute end capable of being thrust into the skin of a human. By gently striking the pressable portion, the acute end of the blade will pierce the skin, for example, that of his or her finger. A small amount of blood for the blood test will ooze out of the skin, and will be taken into a container by using a pipette or capillary. There are many small blood vessels in each finger so that a finger can be pressed to cause a small drop of blood to ooze. Since fingers are more sensitive to pain, it is a recent tendency that the upper arm, abdomen or thigh is subjected to the blood sampling. Similar devices are also used in the latter case too, and an example thereof is disclosed in the U.S. Pat. No. 4,653,513. This device comprises a cylindrical housing and a lancet support, which has a gasket or flexible portion slidably accommodated in the housing. Springs will retract the lancet support to thereby reduce air pressure in the housing so that it sucks a blood sample, automatically and immediately after a lancet pierces the skin.
The gasket in the prior art device is however rigidly secured to the lancet support. The gasket is in air-tight contact with the inner peripheral surface of the housing. Friction between the gasket and said surface will lower the thrust speed of the lancet or needle, thereby increasing pain when the lancet pierces the skin. Further, the lancet support is automatically locked at its position where the skin continues to stick to the device, due to the reduced air pressure. If the cylindrical housing is forced off the skin, then it will spring back and ambient air rushes into the housing. In such an event, blood will scatter or otherwise discharge out of the device, and consequently a somewhat superfluous amount of blood has to be taken.